Alligator shears are powered machines designed to shear, or cut, metal items using a hinged, moving blade passing vertically close up against a second, static blade. The static blade generally makes up or is attached to a flat stage on which the metal object lies when being cut. The alligator shears are typically powered by a hydraulic ram that exercises a single cut per cycle. Older models were, however, driven by electric motors and belts, meaning that the shears operated continuously while the motor was activated. Alligator shears are commonly used in metal fabrication and scrap metal facilities to cut a range of metal items including pipes, bars, and even profile steel such as I-beams.

Cutting metal items during manufacturing operations or the preparation of scrap is generally achieved using an oxy-acetylene torch or an alligator shears. Gas cutting is usually employed on very large or tempered items and the shears used for smaller and softer items. The alligator shears have been a standard fixture in this type of installation for many years and offer a quick and effective metal cutting solution.

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Consisting of a hinged upper blade that moves vertically past a static lower blade, the machine certainly resembles its reptilian namesake. The lower blade is generally part of a large, flat table onto which the metal work piece is laid prior to cutting. When the machine is activated, the upper blade moves down, exercising a scissor-like cutting action. The work piece is then advanced for each consecutive cut. In most cases, a guard descends to enclose the cutting area, preventing accidental amputation or injuries due to work pieces being flung off of the table.

In modern versions of the machine the upper blade is driven by a powerful hydraulic ram that allows for safe, single-cycle operation. Older machines operated with large belt-driven flywheels and ran continuously as long as the drive motor ran. This was not the safest option, as the guard that protected the operator generally lifted to allow for the insertion or movement of the metal being cut. Single-cycle operation allows the alligator's “jaws” to close once only to effect a cut, a far safer option.

These shears are available in a number of sizes, ranging from small, tabletop versions to huge variants capable of exerting several hundred tons of cutting pressure. All have operating limitations regarding maximum work piece sizes and the types of material that may be cut though. In general, very hard, tempered materials such as springs and axles should never be cut with an alligator shears as the blades may be damaged or the items could fracture causing serious injuries.

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